1. Field of the Invention
The present invention relates to probes useful in endoscopy and other procedures, and more particularly to balloon probes adapted to obtain spectroscopic information in the infrared spectral region. The invention also relates to methods that utilize these probes to analyze a surface of interest in connection with the diagnosis and treatment of disease.
2. Description of the Background
Numerous minimally-invasive diagnostic and treatment devices and methods of using them have been developed. Two such categories of devices are endoscopes and balloon catheters.
Endoscopes have proved useful in the examination of internal surfaces, in connection with various surgical and diagnostic procedures. However, conventional endoscopes, such as colonoscopes, gastroscopes, bronchoscopes, and angioscopes, are limited in their ability to detect all pathology present or provide unequivocal identification of abnormalities. These devices typically collect reflected visible light from a lumen, which may be expanded with water or gas, for simple visual evaluation of the tissue surface of interest. If a definitive diagnosis of the type of pathology or disease present in the tissue is needed, a tissue specimen is typically removed or biopsied and submitted for pathologic testing. Unfortunately, the biopsy process increases the risk of complications to the patient, such as hemorrhage, infection, and possible perforation of the organ or vessel under examination.
In addition to endoscopic devices that collect reflected visible light to produce an image allowing for simple visual evaluation, endoscopes that detect fluorescence emitted following excitation of tissue with a radiation source have also been described. One such device includes a visible light source, an optional endoscopic probe, optical sensors, a filter, a detector, and a display monitor. One or two wavelengths of visible light, preferably blue and red/near-infrared light, is directed to the tissue of interest, and remittance and autofluorescence is then detected, integrated/processed and displayed (U.S. Pat. No. 5,590,660 to MacAulay). This device does not incorporate balloons into the probes to facilitate optical coupling, to allow infrared-based evaluation of the diseased tissue.
Another device, useful for diagnosing the condition of GI tissue, utilizes fiber optics to detect emitted fluorescence following excitation radiation treatment (U.S. Pat. No. 5,421,337 to Richards-Kortum). In addition, devices which detect precancerous lesions using a mercury arc lamp endoscope (U.S. Pat. No. 5,647,368 to Zeng), devices which monitor and determine pre-existing physical properties of an organ by excitation with UV light (U.S. Pat. No. 5,456,252 to Vari), and devices which determine bilirubin concentration in tissue using reflectance spectroscopy (U.S. Pat. No. 5,353,790 to Jacques) have also been described. However, these devices do not combine balloon endoscopes with infrared radiation to detect diseased tissue.
Balloon catheters, like endoscopes, have been routinely used for diagnostics and treatment. Typical uses of conventional balloon catheters include procedures such as angioplasty and embolectomy. However, prior to the present invention, these conventional balloon devices could not be used in procedures in which infrared light is emitted in close proximity or directly onto a tissue surface, followed by collection of the light reflected or emitted from the tissue of interest, due to moisture and fluids in the surrounding environment.
The use of infrared radiation in catheters and endoscopic devices is complicated by the fact that water and most bodily fluids are opaque to infrared light. Consequently, even the slightest amount of moisture on the collection end of an endoscopic probe impairs the collection of infrared light. As a result, conventional endoscopes and balloon catheters cannot be used in infrared procedures where moisture or bodily fluids are present.
Fiber optic laser catheters and endoscopes having a protective shield over the probe tip have been described as useful in connection with the diagnosis and removal of atherosclerosis. In one such device, an optical fiber(s) carrying laser radiation is mounted in a catheter having a transparent protective optical shield over its distal end (U.S. Pat. Nos. 5,318,024 and 5,125,404 to Kittrell). The fiber(s) is anchored within the catheter so that there is an appropriate distance or space between the output end of the fiber(s) and the tip of the shield. The intervening space may be filled with fluid, optical surfaces may be optically contacted, or they may be anti-reflection coated to reduce reflections and maximize transmitted light. The catheter may be inserted into a blood vessel and the shield brought into contact with a plaque or obstruction site.
In this device, the protective optical shield mechanically displaces blood at the region to be analyzed and also protects the distal tip of the optical fiber(s) from intra-arterial contents. By locally displacing blood, the shield allows viewing of the tissue of interest without the need for a purge or flush. The optical shield may be in the form of glass, fused silica, sapphire or other optically transparent material. A flexible balloon over the tip of the probe may also be used as an optical shield. A different balloon may be used to provide an anchor point for positioning the catheter during use.
Although the shields of these devices protect a probe tip from blood contaminants, the use of a single balloon to both anchor and protect the tip of the probe from infrared opaque contaminants, which simultaneously allows optical coupling in the infrared region between the probe tip and the tissue surface has not previously been described. The Kittrel devices are designed for use with visible light. In addition, probes incorporating two anchoring balloons which allow the evacuation of a lumen and its subsequent filling with an infrared lucent coupling fluid are also not described.
As can be seen, because of the challenges posed by the effect of moisture on infrared light transmission, available endoscopic devices and catheters are limited in their ability to access and evaluate tissue and/or the lumen of vessels and organs using infrared light. There is therefore a need for a relatively non-invasive device which allows for optical coupling of a probe to the tissue or surface of interest, thereby allowing thorough evaluation and diagnosis of tissues and/or the lumen of vessels and organs using infrared radiation.